This invention relates to sockets for electrical devices and circuitry associated therewith. Although not necessarily so limited, this invention is disclosed in relation to sockets of the type having a cylindrical socket shell contact and a base contact, the socket shell having corrugated threads for receiving the base of a light bulb or other load device.
Typical sockets which receive ordinary lamps with standard screw shell bases are unsafe since a person can insert his finger into an energized socket when the lamp is removed and touch the exposed contacts or terminals therein so as to receive a burn, a painful shock, or an injury. Usually there is no indicator, or an inadequate indicator, of the energized condition of the socket.
Safety sockets have been proposed which permit persons to lightly touch one or both socket contacts where either or both terminals have been de-energized by mechanical means when the lamp has been removed from the socket. Such devices are generally unsatisfactory because if pressure is applied to the same degree as a lamp base would apply pressure when inserted into the socket, the terminals will be re-energized and may cause shock and injury.
Safety sockets have been proposed having electrical terminal contacts retracted by mechanical means from the immediate socket area to preclude accidental contact with energized contacts when the lamp is removed. As the lamp is reinserted into the socket, the retracted terminals reappear in the socket area by the normal pressure of the lamp insertion. Such devices are generally unsatisfactory because if some pressure is applied by a finger of a person in the same manner as a lamp base would provide such pressure when inserted into the socket, the person thus inserting his finger will reactivate the terminals into the socket area and, again, may be subject to possible shock and injury.
Safety sockets have also been proposed where the electrical terminals are located in recesses and must be used with specially designed lamps for insertion into the socket. The recesses which contain the electrical terminal are of sufficiently small size as to provide a person from touching the terminal when a finger is inserted into the socket. Such devices are also generally unsatisfactory because the requirement for specially designed lamp bases limit their usefulness. Usually only one terminal is recessed. In such case, a person may touch the exposed terminal and establish an electrical circuit between the exposed terminal and the ground return and thereby provide the possibility of shock.
Representative safety sockets are shown in the following United States patents:
______________________________________ Inventor Patent No. Issue Date ______________________________________ Nemeth 2,179,797 Nov. 14, 1939 Davis 2,221,345 Nov. 12, 1940 Richards 2,268,061 Dec. 30, 1941 Miller 2,306,741 Dec. 29, 1942 Goldberg 2,439,385 Apr. 13, 1948 Quill 2,688,669 Sept. 7, 1954 Dolph 3,020,366 Feb. 6, 1962 Drago 3,155,788 Nov. 3, 1964 Woodward 3,579,171 May 18, 1971 ______________________________________